1. Field of the Invention
The present invention relates, generally, to a light emitting device light source lens having upper, central and lower parts, and, more particularly, to a light emitting device light source lens having upper, central and lower parts that includes a structure for causing total internal reflections and refraction in light paths extending from the lower part to the upper part, thereby efficiently transmitting light through a side surface.
2. Description of the Related Art
Display and illumination optical systems require light sources that are environment-friendly and have high efficiency and long life spans. Furthermore, with the increase of the efficiency and luminance of Light Emitting Diodes (LEDs), alternative light sources using LEDs have been developed. In particular, as projects such as the development of environment-friendly televisions have been announced, the research and development of Liquid Crystal Devices (LCDs) using LED light sources have been further promoted. In order to meet such technical demand, the need for efficiently shaped LED light source lenses for display and illumination light sources is further increasing.
U.S. Pat. No. 6,679,621 B1 discloses a side emitting LED and the lens thereof. In detail, the patent discloses a lens structure that includes a reflecting surface and refracting surfaces and, thereby, allows light to be emitted from the LED through the side surface of the lens. The lens will be described with reference to FIG. 1 below.
Referring to FIG. 1, a prior art side emitting lens 100 includes an upper part 10 and a lower part 30. The upper part includes a reflecting surface 12 bent symmetrically about the central axis 40 of the lens, and a first refracting surface 14 extended from the end of the reflecting surface at an angle of inclination with respect to the central axis 40. The lower part includes a second refracting surface 32 arcuately extended from the lower end of the first refracting surface 14 to a bottom surface 34.
The light paths based on the prior art side emitting lens 100 are described in the following. Light emitted from an LED light source located at the focal point 50 of the lens 100 can enter the lens through the bottom surface 34 of the lens. Light directly incident on the reflecting surface 12 of the upper part 10 is radiated from the focal point 50, is reflected from the reflecting surface 12 of the upper part 10 to the first refracting surface 14, is refracted at the first refracting surface 14, and is emitted perpendicular to the central axis 40 of the lens (refer to the arrow L1).
Furthermore, light directly incident on the second refracting surface 34 is radiated from the LED light source located at the focal point 50, is refracted by the second refracting surface 34, and is emitted perpendicular to the central axis 40 of the lens (refer to the arrow L2).
As described above, the prior art side emitting lens is characterized in that most of the light is emitted through the first and second refracting surfaces of the lens, so that light radiated from the LED light source is emitted through the side surfaces of the lens.
However, the prior art side emitting lens is problematic in that the end of the reflecting surface of the upper part is sharp, so that light radiated from the LED light source is radiated onto a screen through the sharp portion of the reflecting surface, and it is difficult for light incident on the reflecting surface of the upper part (in particular, a portion of the reflecting surface adjacent to the end thereof) to propagate along a correct light path.
Furthermore, since the end of the reflecting surface of the upper part is sharp, there is concern about deformation due to breakage or damage at the time of mass production. When the lens is deformed, the deformed portion of the lens is located adjacent to a screen, so that the screen may be damaged by the deformed portion.
Meanwhile, the second refracting surface of the lower part functions to minimize the amount of light propagating to the upper part and emit light to the side surface. Since the second refracting surface has a wider area than does the first refracting surface, variation in the curvature of a surface must be high in order to emit light from the second refracting surface at a desired angle, thereby causing the problem of increasing the amount of light confined inside the lens.